Hand held drilling and/or hammering tools are know which can be used with a dust collection unit accessory. The collection unit, may be releaseably mechanically mounted on the tool and will generally comprise a shroud for collecting dust from the region of a tool or bit of the tool, a dust collection chamber, a filter and a system for generating an airflow into and through the shroud, the chamber and the filter. Dust and debris generated by the tool or bit of the tool will be entrained in this airflow and so will be pulled through the shroud and into the chamber. As the air passes through the filter, any dust or debris entrained within it will be deposited in the chamber.
In some known designs of shroud, for example of the type shown on the dust collection unit of FIG. 2, the shroud (32) is mounted on a support arm (36) within which support arm is formed a channel which communicates between the shroud and a dust collection chamber (41). A problem with such designs is that the shroud has an extension (14) for fitment to the support arm (36) which prevents the shroud from fitting into difficult to reach places. For example the shroud cannot easily be positioned so as to fit around pipes or ducting, to drill a hole closer than a distance d1 above the edge of the pipes or ducting and cannot easily be positioned so as to fit into channels with a width less than d2. In addition the shroud (32) is not very effective to collect dust when a hole is to be drilled into a corner as the forward rim of the shroud is adapted to fit to a flat surface and so will not fit the shape of the corner.